Cooley spruce gall adelgid

Adelges cooleyi (Gillette) (Hemiptera Adelgidae)

Orientation to pest

Cooley spruce gall adelgid, Adelges cooleyi (Gillette), is native to the Rocky Mountain region of North America, where it galls various species of spruce (Picea). It is also found in Europe, where it was accidentally introduced through movement of North American conifers for use in plantations, and where it is a pest in plantations of Douglas-fir (Pseudotsuga menziesii [Mirbel] Franco). In North America, damage occurs principally on landscape trees and in plantations. Damage is not important in native forests. Galls are formed on the apical portion of shoot, in contrast to eastern spruce gall adelgid (Adelges abietis [L.]) galls that are found on the basal portion of the twig. Damage is merely aesthetic, but may be economically significant in Christmas tree plantations.

Hosts commonly attacked

The most important host is blue spruce (Picea pungens Engelm.), but other species attacked include white spruce (Picea glauca [Moench] Voss), Sitka spruce (Picea sitchensis [Bong.] Carr.), Engelmann spruce (Picea engelmannii Parry ex Engelm.), and as an alternate host, Douglas-fir (P. menziesii).

Distribution

This species occurs from coast to coast in the northern United States and throughout the range of white spruce in Canada. Populations in the eastern United States where blue spruce planted as an ornamental.

Images of cooley spruce gall adelgid

Whitney Cranshaw, Colorado State University, Bugwood.org 768x512 / 1536x1024	Whitney Cranshaw, Colorado State University, Bugwood.org 768x512 / 1536x1024	Chris Schnepf, University of Idaho, Bugwood.org 768x512 / 1536x1024
Figure 1. Appearance of the large (2-3 cm long) galls caused by Cooley spruce gall adelgid, Adelges cooleyi	Figure 2. Close view of living galls of Cooley spruce gall adelgid	Figure 3. Living galls of Cooley spruce gall adelgid cut in cross section and showing chambers where insects feed
Whitney Cranshaw, Colorado State University, Bugwood.org 768x512 / 1536x1024	Ladd Livingston, Idaho Department of Lands, Bugwood.org 768x512 / 1536x1024	Eric R. Day, Virginia Polytechnic Institute and State University, Bugwood.org 768x512 / 1536x1024
Figure 4. Overwintering adults of Cooley spruce gall adelgid	Figure 5. Appearance of Cooley spruce gall adelgids on its alternate host, Douglas-fir	Figure 6. Heavy infestation on Christmas trees of Cooley spruce gall adelgid. Such trees are not saleable.

Important biological control agents related to this pest species

Little to nothing is known of the natural enemies of this species. Investigations in its native range in the Rocky Mountains of North America may be useful as a source of natural enemies for importation to Europe, where this species is an invasive pest.

Web links for information on cooley spruce gall adelgid

• Fact Sheet | Natural Resources Canada
• Fact Sheet | Ohio State University Extension

Articles

• Lasota, J. A. and D. J. Shetlar. 1986. Assessing seasonal and spatial abundance of Adelges cooleyi (Gillette) (Homoptera: Adelgidae) by various sampling techniques. Environmental Entomology: 15: 254-257.
• Cranshaw, W. S. 1989. Patterns of gall formation by the Cooley spruce gall adelgid on Colorado blue spruce. Journal of Arboriculture 15 (11):277-280.